MATLAB: Error using odearguments??

MATLABode45odearguments

What does this error message mean?

 ??? Error using ==> odearguments at 120
  Inputs must be floats, namely single or double.
Error in ==> ode45 at 172
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...
Error in ==> Testfunction at 32
[t,x] = ode45(@somefn, tspan, x0);

Thanks in advance for any help!

Best Answer

The message means, that the subfunction odearguments recieves non-float values, although it needs this type. The message is actually clear in this point.

Are tspan or x0 both floating point types? You can check this by:

class(tspan)
class(x0)

Related Solutions

MATLAB: Symbols vs Floating points

Your f contains the term "sym('a')". Therefore the results get the type sym also. Perhaps you want to use the command double to make the symbolic expression numerically.

MATLAB: How to solve this ODE 1000 times with random variables

You coded your differential equation correctly. Your ‘x’ variable has only two elements, so you cannot use ‘n’ (or ‘k’) to subscript them.

See if this does what you want:

n = 1000;
result = cell(n,1);
for k=1:n
    tspan=[1 7];A0=rand;P0=rand;g=rand;p=rand;B=rand;
    [t,x] = ode45(@(t,x) [-g*x(1) + p*x(1); -x(1)*x(2)+ B*x(2)], tspan, [A0 P0]);
    result{k} = x;
end

Note that because the time vector can change between your ode45 calls, a cell array is most appropriate. If you want a specific number of values to be returned each iteration, define ‘tspan’ as a vector of more than two elements.

Best Answer

Related Solutions

MATLAB: Symbols vs Floating points

MATLAB: How to solve this ODE 1000 times with random variables

Related Question